Mt Ruapehu eruption

Mount Ruapehu, one of New Zealand’s active volcanoes (scroll down for eruption video) has been at alert level one for some time now. Today scientists announced that the crater lake is continuing to heat up and this has been accompanied by previously unseen seismic activity and other changes in water chemistry and gas output. A yellow alert has been issued to avaiation in the area

Mount Ruapehu is currently experiencing a sustained period of high water temperatures in the Crater Lake (currently about 38 – 39 °C). In recent weeks changes have also occurred in volcanic gas output, seismic activity and Crater Lake water chemistry. These changes show that Ruapehu is experiencing signs of elevated unrest above known background levels, hence the Aviation Colour Code is being raised to Yellow. The Volcanic Alert Level remains at Level 1 (signs of volcanic unrest).

The current heating cycle of the Crater Lake, which started in October 2010, has continued. The temperature of the lake peaked at 41 °C on 1 March and is currently fluctuating around 38 – 39 °C. Since the lake was re-established in 2002, the highest recorded temperature was 42.5 °C in May 2003, and there have been eight heating cycles. The temperature of Crater Lake is a measure of the amount of volcanic heat coming from Ruapehu.

During the current period of high lake temperatures there have also been changes in lake chemistry, increases in carbon dioxide gas emissions and minor increases in seismic activity beneath the volcano. These observations, particularly the seismic activity, have not been observed during previous periods of high lake temperature.

These observations indicate that Ruapehu is experiencing a period of unrest above that which is typical. At times steam may be seen above Crater Lake and sediments on the lake floor may be disturbed by gas and heat flow causing the lake to change colour. However, there are currently no indications that an eruption is imminent.

The elevated unrest is sufficient to raise the Aviation Colour Code to Yellow. This is used only by international aviation. The Volcanic Alert Level is at Level 1 and this already reflects the current state of unrest.

GNS Science volcanologists continue to monitoring Ruapehu. Ruapehu remains an active volcano and future eruptions may occur with little or no warning.

The Volcanic Alert Level remains at Level 1 (departure from typical background surface activity, signs of unrest). The Volcanic Aviation Colour Code is raised to Yellow (elevated unrest above the known background).

Agnes Mazot

The volcano’s present heating cycle started in November 2010 with changes in water temperature, small changes in lake chemistry and minor seismic activity. Geonet said in their 21 February bulletin that “Ruapehu remains an active volcano and future eruptions may occur without warning.”

Video of eruptions in ’95 and ’96

Volcano cam images of the mountain may bee seen HERE and HERE

For more about ash cloud eruptions and disruptions to air traffic in New Zealand please read our two blogs

North Island Eruption Threat “Real” Warns Expert (November 2010)

“An eruption is coming, warns GNS Science volcanologist Dr Graham Leonard, and anyone living pretty much north of Wellington should be prepared.

Leonard is part of a group of volcano experts advising local bodies, emergency services, government agencies and district health boards at a conference in Taupo this week, on how they can best prepare to cope with the aftermath of an eruption.

The venue is deliberately fitting – the Taupo volcanic zone is the most productive volcanic system on Earth. Eruptions, when they happen, are big.

Participants will be told it’s not the lava or the possibility of lahar that Kiwis need worry about, but ash. “Lava flows and lahars are very damaging, but they tend to be local. We spend a lot of time talking about volcanic ash because worldwide it’s the most disruptive and travels a long way.”…”

“Mass Aircraft Grounding Possible In NZ Too, Scientists Say” (April 2010)

“It happened in the mid 1990s and it could easily happen again.

The NZ Geological Survey has issued a press release saying that aviation in New Zealand could also be affected by ash from New Zealand’s active volcanoes and that an eruption the same size as the last one at Lake Taupo could seriously affect 200,000 people in the centre of the North Island.

Mount Ruapehu typically has small eruptions every dozen or so years and larger eruptions about twice a century. Many people will experience it at least once in their lifetimes and should start planning for it because even minor eruptions can cause a lot of problems. In the mid 1990s no-fly zones were declared in the North Island and 11 airports closed, causing disruption to thousands of passengers…

…A more likely threat comes from the cone volcanoes in the Central North Island. Mt Ruapehu typically has small eruptions every dozen or so years and larger eruptions about twice a century.

“It’s definitely worth planning for this type of event because many people will experience it at least once in their lifetime.”

As most of the population lives some distance from New Zealand’s volcanoes, wind-blown volcanic ash will be the most likely hazard people face.”…”

You may also be interested in Earthquakes in Hawkes Bay, 9 September 2010 and Ruapehu’s volcano seismic drum at around that time. This was just five days after the first major quake in Christchurch – the 7.1 magnitude Darfield earthquake.